The objective of this proposal is to utilize the recently developed "Giemsa-trypsin" chromosome banding procedure for enhanced resolution and characterization of chemically induced chromosome aberrations in the newborn offspring of experimental rats and mice. This will be accomplished by the injection of known doses of clastogenic compounds such as Mitomycin-C, triethylenemelamine or 2,3,5- triethyleneiminobenzoquinone-1,4(t) into both male and female rats and mice prior to mating with untreated control animals of the opposite sexes. The effects of both drug and sham treatments on the banded chromosomes of offspring will be compared with the sensitive "translocation heterozygote screening procedure" in order to evaluate the relative merits of the two techniques as in vivo assays for the detection of permanent genetic damage to the offspring of animals exposed to chemical agents. Should the chromosome banding assay prove to be both effective and efficient it would serve as a basis for similar testing of additional chemical compounds and also for the investigation of the role of biologicals and viruses in the production of heritable genetic defects.